1. Field of the Invention
The present invention relates to an electromagnetic solenoid device. More particulary, it relates to an electromagnetic solenoid device used for an electromagnetic valve for power steering control of an automobile.
2. Discussion of the Background
As a device of this kind, there is known an invention disclosed in Japanese Utility Model Unexamined Publication No. 35009/1982. The known device will be described with reference to FIG. 1. In FIG. 1, a reference numeral 1 designates an electromagnetic solenoid device, a numeral 2 designates a solenoid coil, a numeral 3 designates a plunger, a numeral 4 designates a push rod, a numeral 5 designates a control valve for an oil pressure flow path, a numeral 6 designates a spool, a numeral 7 designates a spring bearing, a numeral 8 designates a spring, and characters T, A and P respectively designate oil pressure flow paths.
The operation of the conventional electromagnetic solenoid device will be described.
When the solenoid coil 2 is actuated by feeding current from an external d.c. power source device, the plunger 3 is moved in the direction of the arrow mark to push the push rod 4. A pressing force of the push rod is transmitted to a spool 6 and the spool 6 is caused to slide on the left hand in FIG. 1, compressing the spring 8. During the sliding movement of the spool 6, the oil pressure flow paths T, A and P are changed.
Since the conventional electromagnetic solenoid device is constructed as described above, an attractive force acting on the plunger (a movable iron core) is changed exponentially due to movement (sliding movement in its axial direction) of the plunger. Particularly, when oil pressure flow paths are to be controlled, reliable control can not be obtained.